JP2003110332A - Dielectric antenna, circuit module for high-frequency radio communication, and high-frequency radio communications equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric antenna that can be reduced effectively in physical length and hardly deteriorates in radio-frequency radiation characteristics. SOLUTION: This dielectric antenna 1 has an antenna main body 2, composed of a dielectric substance and has a main surface MP and an antenna wiring pattern 3 provided on the main body 2, in parallel with the main surface MP of the body 2. In the orthogonal projection on the plane of projection which is parallel to the main surface MP, the antenna wiring pattern 3 has a meandering form extended in the length direction O of the antenna 1. In the orthogonal projection, in addition, a wiring width w and a meandering width d of the pattern 3 are adjusted, so that the ratio (d/w) of the meandering width d to the wiring width w becomes >=3, and the absolute value of the meandering width d is adjusted to <=3 mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric antenna preferably used for wireless communication in a high frequency region, a high frequency wireless communication circuit module using the dielectric antenna, and a high frequency wireless communication device. .

[0002]

2. Description of the Related Art Recently, mobile communication devices such as mobile phones and wireless network systems such as wireless LAN and Bluetooth have been rapidly spread. In mobile communication devices, a shift to a high frequency band of 1 GHz or more is remarkable in order to secure a sufficient number of channels as the number of subscribers increases. On the other hand, in the wireless network system, 2.4 GHz band,
Only the frequency bands of 5.2 GHz band, 19 GHz band and 60 GHz band are permitted to be used. Among them, 2.4GH
The z band is used in the majority of wireless network systems because it does not require a user license, is low cost, and has good communication characteristics. However, it is feared that radio resources will be exhausted due to an increase in the number of users in the near future. Active use of the 5.2 GHz band is also expected.

In the wireless communication as described above, the antenna is an indispensable component of the equipment, but it is easy to consume space. On the other hand, in mobile phones and wireless network systems, the tendency toward downsizing of devices has been remarkable in recent years.
Therefore, it is attempted to reduce the size of the entire device by directly forming an antenna pattern on the circuit board or mounting a chip-shaped antenna on the circuit board. In this case, the antenna must be mounted on a substrate with a limited space, so that the size of the antenna must be drastically reduced. In this case, an antenna that does not deteriorate in performance even if it is downsized is naturally required.

In order to miniaturize the antenna, it is effective to use a dielectric. The physical length of the antenna can be shortened to (εr) ^−1/2 when the relative permittivity of the dielectric is εr. Utilizing this, a method of using a circuit module substrate as a dielectric and forming an antenna pattern there, or using a chip antenna in which an antenna pattern and a mounting pad are provided on a dielectric substrate is adopted. . However, in recent years, with the spread of mobile terminals and mobile computers, the demand for miniaturization has become more severe, and it is the current situation that simply using a dielectric material is not sufficient.

[0005]

When the line pattern of the antenna is formed linearly, it causes an increase in the physical length of the antenna, which is not desirable from the viewpoint of miniaturization. Therefore, techniques for bending the line pattern in a meandering form to reduce the antenna length are disclosed in, for example, Japanese Patent No. 3114582, Japanese Patent Laid-Open Nos. 9-55618 and 9-139621.

However, in the above-mentioned conventional dielectric antenna, there is a tendency for the maintenance of the radio wave radiation characteristic to be somewhat neglected due to the pursuit of reduction of the antenna length. An object of the present invention is to form a line pattern in a meandering form, which can effectively reduce the physical length of the antenna, and a dielectric antenna which is less likely to cause deterioration in radio wave radiation characteristics,
A high frequency circuit module and a high frequency wireless communication device using the same are provided.

[0007]

A dielectric antenna according to the present invention comprises an antenna base made of a dielectric material and having a main surface, and an antenna line pattern provided on the antenna base parallel to the main surface. In order to solve the above problems, in orthographic projection on a projection plane parallel to the main surface, the antenna line pattern has a meandering shape extending in the antenna longitudinal direction, and in orthographic projection , W is the line width of the antenna line pattern and d is the meandering width, d / w is 3 or more, and the absolute value of the meandering width d is 3 mm or less.

When the antenna line pattern is formed in a meandering shape, it is geometrically impossible to make the meandering width d smaller than the line width w. Therefore, the smaller the line width w, the finer the meandering can be formed, and the sufficient antenna length reduction effect can be obtained even if the antenna line pattern is small. On the contrary, when the line width w is large, the meandering width must be increased in order to make the antenna length reduction effect sufficient. Therefore, the ratio d / w of the meandering width d and the line width w
Is an indicator of the potential reduction in antenna length.
In the present invention, the first object is to reduce the antenna length, and as a precondition therefor, the value of d / w is set to 3 or more.

From the viewpoint of radio wave radiation, which is the original function of the antenna, it is desirable that the electric field or magnetic field is not locally nonuniform, and it is advantageous that the line pattern be as linear as possible. Therefore, the meandering of the antenna line pattern to reduce the antenna length obviously has a disadvantage in this respect.
The inventors of the present invention have made diligent studies on a line pattern form that does not impair the radio wave radiation efficiency as much as possible and can sufficiently achieve the effect of reducing the antenna length. Can be set to
They have found that they are extremely effective in suppressing the deterioration of radio wave radiation characteristics, and have completed the present invention. As a result, a compact and high-performance dielectric antenna can be realized. In the present invention, the lower limit value of d is not an absolute value but is relatively set in the form of the ratio d / w to the line width w as described above. If the lower limit value (3) is less than,
The desired antenna length reduction effect cannot be achieved sufficiently.

Next, a circuit module for high-frequency wireless communication of the present invention includes at least the dielectric antenna of the present invention and a communication processing circuit for performing transmission processing and / or reception processing of a high-frequency signal via the dielectric antenna. It is characterized in that a mounting component forming a part is integrated by a component mounting board. A high frequency wireless communication apparatus of the present invention is characterized by including the above-mentioned dielectric antenna of the present invention and a communication processing circuit that performs transmission processing and / or reception processing of a high frequency signal via the dielectric antenna. .

By using the dielectric antenna of the present invention in a high frequency wireless communication device or a high frequency wireless communication circuit module, it is possible to make the circuit module or the entire device compact, and to meet the recent demand for severe downsizing. Will also be able to respond adequately. Further, despite the small size of the built-in antenna, good antenna radiation characteristics are maintained, and as a result, a small, lightweight, and highly sensitive wireless communication device can be realized.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. 1A and 1B show a dielectric antenna 1 according to an embodiment of the present invention, in which FIG. 1A is a side view and FIG.
Is a plan view and (c) is a bottom view. Dielectric antenna 1
Is an antenna substrate 2 made of a dielectric material and having a main surface MP.
And an antenna line pattern 3 provided on the antenna base 2 in parallel with the main surface. The antenna line pattern 3 has a projection plane PP parallel to the main surface MP.
In orthographic projection with respect to, it has a meandering form extending in the antenna length direction.

More specifically, as shown in FIG.
Each is formed in a direction intersecting with the antenna length direction (O),
Further, it has a plurality of cross direction line units 32 arranged in the antenna length direction. These cross-direction line units 32 are formed by connecting the adjacent ends in an alternating manner and forming a meandering continuous line portion as a whole.

As shown in FIG. 1, by forming the antenna line pattern 3 in a meandering shape, the antenna length L (which is the longitudinal dimension of the antenna base 2) can be effectively reduced. However, as is clear from FIG. 2A, it is geometrically impossible to make the meandering width d smaller than the line width w. Therefore, as shown in FIG. 2B, it becomes possible to form finer meanders as the line width w becomes smaller, and a sufficient antenna length reduction effect can be obtained even if the meandering width d is small. In the present invention, the value of d / w is set to 3 or more as a precondition. And the track width w
Regardless of, the absolute value of the meandering width d is set to 3 mm or less. As a result, it is possible to effectively suppress the deterioration of the radio wave radiation characteristic of the antenna 1 despite the use of the meandering pattern, and it is possible to realize a compact and high-performance dielectric antenna.

In the antenna line pattern 3 of FIG. 2, a plurality of intersecting direction line units 32 are formed in a direction orthogonal to the antenna length direction, and are arranged in the antenna length direction. Unit 32), and further has a connecting line unit 33 in which antennas that alternately connect the ends of adjacent orthogonal direction line units 32 are formed in parallel with the longitudinal direction. Orthogonal line unit 32
Has the advantage that the effect of reducing the antenna length is great because the dimension occupied length in the antenna length direction becomes equal to the line width w which is the limit value. However, the form of the antenna line pattern in the present invention is not limited to this. For example, an antenna line pattern in which inclined cross-direction line units are alternately connected by a connection line unit parallel to the antenna length direction, an antenna line pattern in which cross-direction line units are smoothly connected in a sinusoidal curve shape, and the like are conceivable. . These antenna line patterns are inferior to those in FIG. 2 in terms of the effect of reducing the antenna length, but they have an advantage that radio wave radiation loss can be reduced because no acute-angled bent portion is generated.

In FIG. 8, an alumina sintered body (thickness: 1 mm) is used as a dielectric material forming the antenna base 2, and the line width w of the dielectric antenna is set to a resonance frequency of 2.4 GHz. It shows the relationship with the antenna length. However, the meandering width d is set to 2 mm, and the facing edge interval s of the orthogonal direction line unit 32 (defined as the distance between the facing edges).
Is set equal to the track width w. According to this, it is understood that the antenna length can be remarkably shortened as the line width w of the antenna line pattern 3 becomes smaller.

As a typical conventional antenna, when a monopole antenna is formed on a component mounting printed circuit board, the antenna length at which the resonance frequency is 2.4 GHz is 27.
reach mm. In the present invention using a meandering line pattern, according to FIG. 8, if a line width of 0.3 mm or less is adopted, it is about half (13.5 m) of a monopole antenna.
It can be seen that the antenna length can be shortened to m). However,
When the line width w is less than 0.05 mm, the characteristic impedance of the antenna increases due to an increase in the inductance component, and impedance mismatch with the communication circuit side to which the antenna is connected leads to a problem that the radio wave radiation efficiency decreases. Therefore, the line width w is preferably set to 0.05 mm or more.

In FIG. 1, the antenna line pattern 3 is
The whole is arranged on the main surface MP of the antenna base 2. When the antenna base 2 is made of a sintered ceramic dielectric, the antenna line pattern 3 can be made of a refractory metal such as platinum and can be manufactured by cofiring with the ceramic dielectric. However, since the line metal material of the antenna line pattern 3 must be made of an expensive refractory metal, there is a problem that the cost tends to increase. Therefore, if a method of forming the antenna line pattern 3 by secondary metallizing treatment on the main surface MP of the antenna base 2 after firing the antenna base 2 is adopted, a line metal material having a lower melting point can be adopted, It is economical. Specifically, a pattern is printed and formed on the antenna base body 2 after firing using a metal paste having a relatively low melting point such as Ag, and the metal paste is sintered at a lower temperature than when firing the dielectric. A method of performing secondary firing at a temperature at which it sufficiently proceeds can be exemplified. In addition, a line pattern can be formed by a chemical plating method, a physical vapor deposition method, or the like. Specifically, Ag-based (Ag simple substance, A
g-Metal oxide (oxide of Mn, V, Bi, Al, Si, Cu, etc.), Ag-glass addition, Ag-Pd, Ag-P
t, Ag-Rh, etc.), Cu-based (Cu simple substance, Cu-metal oxide, Cu-Pd, Cu-Pt, Cu-Rh, etc.) and other low resistance materials can be used. As shown in FIG. 1 (a), the antenna line pattern 3 formed on the main surface MP of the antenna substrate 2 is covered with a protective dielectric layer 7 (thickness) made of a low temperature firing type ceramic such as polymer or glass ceramic. (For example, about 5 to 50 μm)
It can also be covered by.

In the dielectric antenna of the present invention, as shown in FIG. 3, the antenna line pattern 3 is divided into laminated segments 3s, and the antenna substrate 2 is formed as a laminated body.
It is also possible to have a configuration in which the layers are dispersedly arranged. Each laminated segment 3s is connected by a conductive via 3v.
By doing so, it is possible to realize antenna directivity that is not biased to the main surface MP.

Further, in FIG. 2, the facing edge spacing s of the adjacent orthogonal direction line units 32, 32 is at least 0.1 m.
It is desirable to secure at least m in order to secure good radio wave radiation characteristics. On the other hand, the facing edge spacing s is set to 2 of the line width w in order to make the antenna length reduction effect remarkable.
It is desirable to keep the range below twice. In the orthographic projection of the antenna line pattern 3, the opposite edge interval s is defined as the opposite edge of the adjacent orthogonal direction line units 32, 32 is
It is defined as the length to cut out the center line O with respect to the meandering width d (see also FIG. 3).

The results of experiments conducted to investigate the influence of the meandering width d will be described below. First, an alumina sintered body (thickness: 1 mm) is used as a dielectric that forms the antenna base 2.
Was used, and dielectric antennas in which the total length of the line was set to 30 mm were produced as those having various meandering widths d, line widths w, and opposed edge intervals s. These antennas are connected to a commercially available network analyzer (HP-8510C manufactured by Yokogawa Hewlett-Packard Co., Ltd.),
The reflection coefficient S ₁₁ at 2.4 GHz was measured. Figure 6
The results are shown in. Table 1 summarizes the individual measurement point data in FIG.

[0022]

[Table 1]

According to this, the line width w and the facing edge spacing s
Irrespective of the above, as the line width w is reduced, the reflection coefficient S
_It can be seen that ₁₁ is reduced and the radio wave radiation efficiency is improved. It can be seen that by setting the meandering width d to 3 mm or less, a sufficient antenna gain of -8 dB or less can be achieved.

Next, with respect to the dielectric material forming the antenna base 2, the effect of reducing the antenna length is increased as the relative permittivity is increased. However, if the relative dielectric constant is excessively increased, the radio wave radiation efficiency is lowered, or no load is applied. The increase in the bandwidth may lead to a problem that the bandwidth is reduced. From this viewpoint, it is desirable to use a material having a relative dielectric constant of 13 or less at 2.4 GHz for the dielectric body forming the antenna substrate 2. As such a dielectric material, alumina ceramics, mullite ceramics, glass ceramics or the like having an alumina content of 98% or more are preferably used in the present invention as a material having a small dielectric loss even in a high frequency region. It As the glass ceramic, a system in which 40 to 60 parts by weight of an inorganic ceramic filler such as alumina is added to borosilicate glass or lead borosilicate glass,
The simultaneous sinterability with the metal line portion is good, which is preferable. Also,
Other than ceramic dielectrics, inorganic / polymer composites such as glass epoxy materials can be used.

The results of experiments conducted to investigate the influence of the relative dielectric constant will be described below. As the antenna base 2 of the dielectric antenna of the type shown in FIG. 1, the following materials were prepared (all having a thickness of 1 mm):-Titania-based dielectric (relative permittivity at 2.4 GHz:
21);-Alumina-based dielectric (relative permittivity at 2.4 GHz:
13);-Glass ceramics-based dielectric (relative permittivity at 2.4 GHz: 8);-Glass epoxy resin-based dielectric (relative permittivity at 2.4 GHz: 4).

Using the above-mentioned antenna substrate 2, the meandering width d is set to 2 mm, the opposing edge spacing s of the orthogonal direction line unit 32 is set to be equal to the line width w, and the total line length has a resonance frequency of 2.4 GH.
Various dielectric antennas optimized to have z were manufactured. These antennas were connected to the network analyzer, and the reflection coefficient S ₁₁ at 2.4 GHz was measured. The result is shown in FIG. According to this, it is understood that the smaller the relative permittivity of the antenna substrate 2 is, the smaller the reflection coefficient S ₁₁ is, and the radio wave radiation efficiency is improved. It can be seen that by setting the relative permittivity to 13 or less, a sufficient antenna gain of -8 dB or less can be achieved.

Various application modes of the dielectric antenna of the present invention will be described below. Dielectric antenna 1 of FIG.
Is formed in the shape of an elongated rectangular parallelepiped in which the longitudinal direction L coincides with the antenna longitudinal direction, and one of the two ridgeline directions orthogonal to the longitudinal direction L is the thickness direction T, and in the thickness direction T The antenna line pattern 3 is formed in parallel with the main surface MP. Then, the surface mounting pad 5 that is electrically connected to the antenna line pattern 3 is formed on one side MP ′ of the two main surfaces to constitute a chip antenna. By applying the present invention to such a chip antenna, it is possible to effectively reduce the size of the chip antenna, and easily secure a mounting space even in a component mounting board whose area is reduced due to downsizing of equipment. It becomes possible to do. In FIG. 1, the antenna line pattern 3 is formed on one main surface MP in the thickness direction T, and the surface mounting pad 5 is formed on the other main surface (hereinafter, referred to as back surface) MP ′. The surface mounting pad 5 is electrically connected to the antenna line pattern 3 via the side surface via 4. Further, as shown in FIG. 1C, an auxiliary pad 6 is formed on the back surface MP ′ of the antenna base 2 and is joined to the substrate 41 together with the pad 5 using the solder joint portion 9.

On the other hand, as shown in FIG. 4, the antenna substrate may be formed by diverting a part of the component mounting board 41. In this case, the antenna line pattern 3 is directly formed on the surface of the substrate 41 made of a dielectric material. According to the present invention, since the length of the antenna line pattern 3 can be effectively reduced, the component mounting board 41 having a reduced area can be obtained.
Also in this case, it is possible to easily secure a space for forming the antenna line pattern 3.

FIG. 5 shows an example of the circuit configuration of a high frequency radio communication device using the dielectric antenna of the present invention. This device 50 communicates with the dielectric antenna 1 and performs radio transmission / reception processing of a high-frequency signal via the dielectric antenna 1 (dedicated to transmission or reception as required). And a processing circuit 49.
The communication processing circuit 49 has a receiving circuit 46 and a transmitting circuit 45, and the dielectric antenna 1 is selectively connected to either of them by an antenna switch 56.

The operation at the time of reception is as follows. That is, the radio wave signal (for example, center frequency 2.4 GHz) received by the dielectric antenna 1 is transmitted by the antenna switch 56.
The signal in the unnecessary frequency band is removed by the low-noise amplifier 62 via the reception side bandpass filter 61, and the output of the removed signal and the local oscillator 57 is mixed by the mixer 60. Then, the modulated signal (IF signal) generated by the mix is IF
A component (for example, 10
0 to 300 MHz) is taken out, demodulated by the demodulation circuit 58, and then input to the baseband circuit 51.

On the other hand, the operation during transmission is as follows.
The source signal from the baseband circuit 51 is a low-frequency analog or digital signal, and the modulation circuit 52 uses the source signal to generate a carrier wave (for example, 100 to 300).
Mhz) is modulated and further mixed with the output signal of the local oscillator 57 by the mixer 53. A component (for example, a center frequency of 2.4 GHz) of a required band is extracted by the transmission side band pass filter 54 from a plurality of resulting modulated signals, amplified by a power amplifier 55, and then passed through an antenna switch 56 to obtain a dielectric antenna. Sent from 1.

The circuit configuration shown in FIG. 5 is applied to a mobile phone or a wireless LA.
It can be used as a basic part of communication devices for wireless network systems such as N and Bluetooth.

The circuit of the high frequency radio communication device of FIG. 5 is shown in FIG.
As shown in FIG. 3, the circuit module 4 in which the dielectric antenna 1 and other mounting components 43 are mounted on the component mounting substrate 41.
It can be configured as zero. In this case, all of the circuit components shown in FIG. 5 may be mounted on the circuit module 40, or a part of the circuit module 40 other than the dielectric antenna 1 may be mounted outside the circuit module 40. May be provided separately. Further, peripheral mounting components not shown in FIG. 5 may be mounted on the Bluetooth module. Reference numeral "42" is a connector for mounting the module 40 in a slot of a mother board or the like.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a dielectric antenna of the present invention together with a mounted state.

FIG. 2 is an explanatory diagram showing an example of an antenna line pattern of the dielectric antenna of FIG.

FIG. 3 is an explanatory view showing another modification of the antenna line pattern.

FIG. 4 is a perspective view schematically showing an example of a circuit module for a high frequency wireless communication device of the present invention.

FIG. 5 is a circuit diagram showing an example of a high frequency wireless communication device using the dielectric antenna of the present invention.

FIG. 6 is a meandering width of an antenna line pattern and a reflection coefficient S1.
The graph which shows the experimental result which measured the relationship with 1.

FIG. 7 is a graph showing the experimental results of measuring the relationship between the relative permittivity of the dielectric material used for the antenna substrate and the reflection coefficient S11.

FIG. 8 is a graph showing the relationship between the line width of the antenna line pattern and the antenna length.

[Explanation of symbols]

1 Dielectric antenna 2 Antenna base 3 antenna line pattern 40 Circuit module for high frequency wireless communication 41 Component mounting board 43 Mounted parts 45 Transmission circuit (communication processing circuit) 46 Receiver circuit (communication processing circuit) 50 high frequency wireless communication device

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5J045 AA05 AB05 DA09 EA08 HA03                       LA03 NA03                 5J046 AA03 AA07 AB13 PA04                 5J047 AA03 AA07 AB13 FD01

Claims (8)

[Claims] 1. A dielectric antenna having an antenna base body made of a dielectric material and having a main surface, and an antenna line pattern provided on the antenna base body in parallel with the main surface, wherein a projection parallel to the main surface is provided. In orthographic projection on a plane,
The antenna line pattern has a meandering shape extending in the antenna length direction, and in the orthographic projection, the line width of the antenna line pattern is w and the meandering width is d.
d / w is 3 or more, and the absolute value of the meandering width d is 3
A dielectric antenna characterized by being less than or equal to mm. 2. The antenna line pattern has a plurality of orthogonal direction line units each formed in a direction orthogonal to the antenna length direction and arranged in the antenna length direction, and further includes adjacent orthogonal direction line units. The dielectric antenna according to claim 1, wherein connecting line units connecting the ends in an alternating manner are formed parallel to the antenna length direction. 3. The dielectric antenna according to claim 1, wherein the line width w of the antenna line pattern is 0.3 mm or less. 4. The dielectric body forming the antenna base,
The dielectric antenna according to claim 1, wherein a material having a relative permittivity of 13 or less at 2.4 GHz is used. 5. The main surface in the thickness direction, wherein the antenna base is formed in a rectangular parallelepiped shape whose longitudinal direction coincides with the antenna longitudinal direction, and one of two ridgeline directions orthogonal to the longitudinal direction is set as the thickness direction. 5. The chip antenna according to claim 1, wherein the antenna line pattern is formed in parallel with and a surface mounting pad that is electrically connected to the antenna line pattern is formed on one side of two main surfaces. The dielectric antenna according to item 1. 6. The dielectric antenna according to claim 1, wherein the antenna base is formed by diverting a part of a component mounting board. 7. The dielectric antenna according to claim 1, and at least a part of a communication processing circuit that performs transmission processing and / or reception processing of a high-frequency signal via the dielectric antenna. A circuit module for high-frequency wireless communication, characterized in that the mounted component is integrated with a component mounting board. 8. A dielectric antenna according to any one of claims 1 to 6, and a communication processing circuit for performing transmission processing and / or reception processing of a high-frequency signal via the dielectric antenna. Characteristic high-frequency wireless communication device.